Plants and methods of thawing deep-frozen products are known in various designs. The disclosure of EP-A-0 298 063 thus deals with a thawing-out method whereby air sweeping around the product is kept saturated with water vapour by adding atomized water at a specific temperature, thereby also controlling the temperature of the air. The thawing-out is stopped when the temperature in the middle of the product has risen to a predetermined value.
However, it is not all types of products that can be thawed out by means of humid air. Such a method causes water to condense on the product. This is desirable in certain cases (thawing out unpacked fish or meat), but in other cases it cannot be allowed, e.g. when thawing out products packed in materials soluble in water. GB patent No. 2 044 906 A thus discloses such a method according to which the temperature of the air sweeping around the product is controlled and thereby kept at a value a few centigrades above the temperature of the product in order to avoid moisture condensation on the product.
Various other systems and methods of thawing frozen products are known. The common features are that the air sweeping around the product is controlled to a larger or smaller degree in respect of temperature and water content and that the thawing is interrupted after a predetermined period or when the temperature in the middle of the product (the core temperature) has risen a predetermined value.
With respect to the thawing of a frozen product there are various demands to consider: A frequent interest is taken in that the thawing is effected as quickly as possible whereas, on the other hand, the temperature of the product must not locally rise so much that bacteria get favourable conditions of growth, thereby damaging the product.
The purpose of the invention is to comply with said requirements as well as possible.